pagemap: fix bug in add_to_pagemap, require aligned-length reads of /proc/pid/pagemap

Fix a bug in add_to_pagemap.  Previously, since pm->out was a char *,
put_user was only copying 1 byte of every PFN, resulting in the top 7
bytes of each PFN not being copied.  By requiring that reads be a multiple
of 8 bytes, I can make pm->out and pm->end u64*s instead of char*s, which
makes put_user work properly, and also simplifies the logic in
add_to_pagemap a bit.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Thomas Tuttle <ttuttle@google.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 19 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 88717c0f941b..17403629e330 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -496,7 +496,7 @@ const struct file_operations proc_clear_refs_operations = {
 };
 
 struct pagemapread {
-        char __user *out, *end;
+        u64 __user *out, *end;
 };
 
 #define PM_ENTRY_BYTES      sizeof(u64)
@@ -519,21 +519,11 @@ struct pagemapread {
 static int add_to_pagemap(unsigned long addr, u64 pfn,
                           struct pagemapread *pm)
 {
-        /*
-         * Make sure there's room in the buffer for an
-         * entire entry.  Otherwise, only copy part of
-         * the pfn.
-         */
-        if (pm->out + PM_ENTRY_BYTES >= pm->end) {
-                if (copy_to_user(pm->out, &pfn, pm->end - pm->out))
-                        return -EFAULT;
-                pm->out = pm->end;
-                return PM_END_OF_BUFFER;
-        }
-
         if (put_user(pfn, pm->out))
                 return -EFAULT;
-        pm->out += PM_ENTRY_BYTES;
+        pm->out++;
+        if (pm->out >= pm->end)
+                return PM_END_OF_BUFFER;
         return 0;
 }
 
@@ -634,7 +624,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 
         ret = -EINVAL;
         /* file position must be aligned */
-        if (*ppos % PM_ENTRY_BYTES)
+        if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
                 goto out_task;
 
         ret = 0;
@@ -664,8 +654,8 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                 goto out_pages;
         }
 
-        pm.out = buf;
-        pm.end = buf + count;
+        pm.out = (u64 *)buf;
+        pm.end = (u64 *)(buf + count);
 
         if (!ptrace_may_attach(task)) {
                 ret = -EIO;
@@ -690,9 +680,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                 if (ret == PM_END_OF_BUFFER)
                         ret = 0;
                 /* don't need mmap_sem for these, but this looks cleaner */
-                *ppos += pm.out - buf;
+                *ppos += (char *)pm.out - buf;
                 if (!ret)
-                        ret = pm.out - buf;
+                        ret = (char *)pm.out - buf;
         }
 
 out_pages: